The present invention relates to a printing apparatus for printing a variety of information such as images and characters on a recording medium such as a card. More particularly, the present invention relates to a printing apparatus capable of switching printing methods for transferring a variety of information to a surface of a recording medium or a transfer medium to form images thereon.
Conventionally, when card-shaped recording media such as credit cards, cash cards, license cards, and ID cards are produced, a transfer type printing apparatus is used for thermally transferring desired images and characters to a recording medium via a thermal transfer sheet with a thermal head to print the images. As an example, in Japanese Patent Publication (Kokai) No. 09-131930 (corresponding to U.S. Pat. No. 5,959,278), a printing apparatus of a direct transfer type directly transfers images and characters to a recording medium via a thermal transfer sheet. In this method, a thermal sublimate ink is used due to superior color tones, thereby attaining high quality images. However, it is necessary to provide a receptive layer on a surface of a recording medium to which images are transferred for receiving ink, thereby limiting a type of recording medium, or making it necessary to form the receptive layer on a surface of a recording medium.
Generally, as a recording medium capable of receiving a thermal sublimate ink, cards made of polyvinyl chloride (also known as PVC cards) have been widely used. However, since harmful substances are generated when such cards are incinerated, there has been a trend of switching to cards made of polyethylene terephthalate (also known as PET cards). Furthermore, in recent years, card-shaped media embedded with IC chips or antennae have been used in a variety of fields. Because an object is embedded in such a card, the card has an uneven surface, thereby making it difficult to transfer an image.
In order to solve the problems described above, Japanese Patent Publication (Kokai) No. 11-348328 has disclosed technology of a thermal transfer type printing apparatus, so-called an indirect transfer type printing apparatus, in which an image is formed on an intermediate transfer medium once, and is then transferred to a recording medium. In the indirect transfer method, it is possible to transfer an image to an uneven surface of a recording medium without limitation in card types associated with the receptive layer, i.e. disadvantages of the direct transfer printing method. Furthermore, it is easy to print an entire surface of the card-shaped recording medium compared to the direct transfer method.
However, in the indirect transfer method, it is necessary to use an intermediate transfer medium, thereby increasing running cost and printing time compared to the direct transfer method. Furthermore, depending on a design of the card, even if an entire front surface needs to be printed, only limited area of a backside is used for printing a text such as a precaution of the card in many cases. There are limited cases requiring printing the entire both surfaces, so there are merits and demerits associated with both methods of printing.
Therefore, depending on a material of the recording medium such as PVC and PET, and a characteristic and an printing purpose of the recording medium including an IC element, it is desirable that a printing apparatus can switch between the direct transfer method and the indirect transfer method to print images to a recording medium. With such a printing apparatus, it is possible to print with a method best suited for a specific recording medium and reduce running cost associated with the printing. Therefore, such a printing apparatus will be widely used in the future.
In a printing apparatus of the indirect transfer method described above, an intermediate transfer medium with a film shape is accurately placed on a platen roller arranged opposite to a thermal head, i.e. a member for forming an image. Then, the intermediate transfer medium is moved back and forth several times to form an image thereon. At this time, a roller member (clamp roller) may be provided for nipping and guiding the intermediate transfer medium with the platen roller, so that the intermediate transfer medium moves stably and accurately (refer to Japanese Patent Publication (Kokai) No. 11-348328). It is not necessary to provide such a roller member in a printing apparatus of the direct transfer method, in which an image is directly transferred to the recording medium such as a card.
Moreover, it is conceivable that a foreign material may be adhered to the roller member and transferred to a surface of the platen roller. In such a case, when an image is formed on the recording medium formed of a flexible material with the direct transfer method, the foreign material adhered to the platen roller forms an uneven portion on the recording medium, thereby causing improper image transfer. Such a problem may occur in the indirect transfer method as well when an image is formed on the recording medium with a film shape.
Specifically, in the printing apparatus capable of printing images to the recording medium by switching between the direct transfer method and the indirect transfer method as described above, to obtain proper images without the transfer problem, it is necessary to disable the function required for the indirect transfer method when the direct transfer method is used.
Furthermore, in the indirect transfer method, when the intermediate transfer medium is replaced, if the intermediate transfer medium set at a predetermined refilling position is shifted improperly, the intermediate transfer medium moves irregularly when an image subsequently is formed. In this case, it is necessary to correct the improper and weaving movement to an appropriate state.
In view of the problems described above, an object of the present invention is to provide a printing apparatus capable of printing images to a recording medium by switching between the direct transfer method and the indirect transfer method for convenience of a user, in which it is possible to print with a method best suited for the recording medium, thereby reducing running cost associated with the printing.
Another object of the present invention is to provide a printing apparatus in which it is possible to reduce a problem of improper transfer both in the direct transfer method and the indirect transfer method.
Further objects and advantages of the invention will be apparent from the following description of the invention.